Drill bit with nontracking rollers



4o ceed over the formation.

Patented Dec. 31

" UNITED u STATES PATENT) OFFICE mum. arr WITH nomscmue ROLLERS John A. Zublin, 1.... Angeles, Calif. Application May 13, 1940, Serial No. 334,809

5 Claims.

5 Bits of the type illustrated in Patent 2,126,079,

granted August 9, 1938, cut a pattern in the formation very similar to that shown in Figure 3 of the patent. If the rollers are evenly spaced, and the discs of the cutters are evenly Spaced on the rollers, there is a tendency for the carrier to take up such a position with relation to the formation as to cause the rollers to track, 1. e.,

for the rollers to follow the pattern as the bit rotates. Of course, the pattern is composed of two sets of lines, one set extending spirally downward, and the other set extending spirally upwards, as shown in Figure 3-0! the patent 'referred to, but the two patterns do not obliterate each other in certain types of formation. Attempts to remedy the tendency to track by uneven spacing of the rollers, and uneven spacing of the discs on the rollers, have to some extent limited the tracking tendency, but it is obvious that variation in spacing decreases the amount or cutting edge available, as there is a minimum distance between rollers, imposed by the cutting action on the formation. With these limitations in mind, it is proposed-to modify the cutting action of a bit of the type above-mentioned to bring about a more complete breaking up of the pattern than has heretofore been possible.

, It is therefore a primary object of this invention to prevent tracking of cutters in a rolling disc bit.

It is a further object of the-present invention to vary the paths any given roller takes over the formation. l

It is a further object of this'invention to cause the cutters to take difierent paths-as they pro- It is a further object of the present invention to introduce a variation in the motion of a cutter across the formation to introduce a diflerent cutting action. F

Referring now to the drawing: 1

Figure 1 is an elevation. partly in section, of oneform of bit embodying the present invention;

Figure 2 is Figure 1; and

, Figure 3 is a diagram rot-the bottom of a bore being produced by the bit of Figure 1, illustrating the paths .0! the cutters.

A shank Ii is provided with a pin ii for en-- a side view or the bit shown in .gagement with the drill collar and the rest of the drilling string. A series of reamers, i2, i3 and i4 is mounted on the shank for rotation, in any manner desired. The shown mounting ;is, by means of a series of plates welded into slots in the shank, as fully described. in ,U. S. Patent .5 2,156,444, granted May 2, 1939. These reamers are for the dual purpose orlinsuring a full gauge bore and for proper positioning of the cutter head with respect to the bore, to cause the head to rotate on the shank.

Below the reamers is provided a leg l5, having a bearing support ll extending therefrom. A sleeve I1 is mounted on the bearing support I6, which sleeve ilhas ball races l2 and a roller race I! on its outersuriace. In order to provide a convenient method of assembly for the ball bearings, there is an opening through the sleeve intersectihgeach ball race for the insertion of balls, the opening being closed with .the plug 2i). This plug has its lower portion formed to act as a key, resting in a keyway formed in the bearing support, to prevent the sleeve II from rotating on the bearing support I.

A carrier 2|, with its inner bore formed to cooperate with the ball. and roller races of the sleeve I1 is mounted on the sleeve II, and rotates freely therearound. This carrier 2| in turn carries a series'oi rolling cutters 22 of the type v referred to in the above mentioned Patent No. 2,126,079. These rolling cutters 22 have on their faces cutting teeth 22, here illustrated as a series 1 of discs, suitably hardfaced or otherwise treated to make them capable of penetrating the formation being cut. To secure the carrierin place, and also provide additional support for the hearing support it, a leg 2i is welded or otherwise secured to the shank and carries the support It in a hole near its lowermost end.

To this point, the described bit is largely conventional. InFigure 1. it will be noted that line A-A. is perpendicular to the bearings between the sleeve and the carrierrLine B-B passes. through the centers of the cutters 22, and might be. said to represent the plane of the cutters. 0-0 is the same number of degrees from A- A as 3-8, but on the other side. It the carrier 21 is rotated degrees i'rom its position shown in Figure 1, the line through the centers of the cutters would take the position of line 0-6, and the cutterwould .take the position of the dotted circle 22'.

In Figure 8 is shown, in section, the bottom of share being produced by thisbit. Ar'explained in thepatent above referred to, the cutters roll about the hemispherical bowl along a line such 55 as 3ll. 1 the-following cutters run" on lines which can best be described as parallel to line 30, as shown in Patent 2,126,079; and, at the same time, the cutters on the rising side of the carrier cut a series of spirals in the'other direction. As was said in the onset, it is sometimes difficult to prevent the cutters from tracking in the pattern as the bit rotates. With the cutters set in other than the plane of A--A, however, each cutter takes, or tends to take,.a slightly different path from the others. For instance, the lowermost cutter of Figure 1 will travel over the solid line", while the uppermost cutter will, if started from the same point in the hemisphere, travel along the dotted line 3|. This is so because the constants which determine the path of the cutter, as for example, the distance of the plane of rotation of the cutter from the axis of the hole, (and, incidentally, fromthe bit axis) are different for each cutter, the top and bottom cutters of Figure 1 having the two extremes of motion.

It is readily apparent that a fan of lines at comparatively. small angles to each other, be-

' tween 30 and 3|, would be most eflicacious in obliterating the pattern generated by the rollers as they cut into the formation. In practice, it has been found that the cutters, when arranged as described, exhibit the characteristic wear of cutters working on a patternless, or slightly patterned, hole bottom. At the same time, the bit cuts faster and further before worn out, due to the improved action of the cutters and the diminished tracking tendency of the cutters.

It is to be understood, of course, that thescope of the present invention is to be determined from the appended claims, and not from the description above, which is intended to be illustrative only.

What I claim as my invention is:'

1. In an earth boring bit, a shank, a carrier mounted for rotation on said shank, a series of rolling cutters mounted for rotation on said carrier, said cutters being so arranged that their 5 centers are at varying distances from a plane perpendicular to the axis of rotation of the shank.

2. In an earth boring bit, a shank, a carrier mounted for rotation on said shank, a series of rolling cutters mounted for rotation on said carreamers holding said shank with its axis a Predetermined distance from the walls or the bore being produced, a carrier mounted for rotation on said shank, and a series of rolling cutters mounted ior rotation on said carrier, said cutters being mounted with their axes in a common plane inclined with respect to the axis of rotation of the carrier.

4. A carrier assembly for earth boring bits comprising a carrier body, a series of cutters mounted for rotation on said carrier body, and bearing means for rotatable mounting of said carrier, said series. of cutters being mounted with their axes in a common plane inclined with respect to the axis of said bearing means.

5. A carrier assembly for earth boring bits cOmprising a carrier body, a series of cutters mounted for rotation on said carrier body, and bearing means for rotatable mounting of said carrier, said series of cutters being mounted with their centers atvarying distances from a plane perpendicular to the axis of said bearing means.-

' Join: A. znnnm. 

